Infants and other incontinent individuals wear absorbent articles such as diapers to receive and contain urine and other body exudates. Absorbent articles function both to contain the discharged materials and to isolate these materials from the body of the wearer and from the wearer's garments and bed clothing. Disposable absorbent articles having many different basic designs are known to the art. For example, U.S. Pat. No. Re. 26,152, issued to Duncan and Baker on Jan. 31, 1967, describes a disposable diaper which has achieved wide acceptance and commercial success. U.S. Pat. No. 3,860,003, issued to Buell on Jan. 14, 1975, describes an elasticized leg cuff disposable diaper which has achieved wide acceptance and commercial success.
However, absorbent articles of the current art have a tendency to sag or gap away from and to slide/slip down on the body of the wearer during wear. Three modes of failure have been identified which contribute to this sagging, gapping, sliding, and slipping:
1) Forces exerted by the normal movement of a wearer as the wearer breathes, moves and changes position can cause the waist region of a diaper to rollover during normal use resulting in a reduced gasketing effect at the waist. PA1 2) Normal wearer movement can cause the band of lateral tension created by the absorbent article's fastening system to ride down below the belly to the belly crease of the wearer. This is because of the fact that, for an irregularly shaped volume, a band of tension will seek the cross-section having the minimum circumference for that volume. Typically, absorbent articles are fastened about the waist of a wearer at or near the wearer's navel, while the minimum circumference around a wearer goes through a point slightly below the wearer's belly, at the belly crease, and through a point at the small of the back. As a result, the band of tension will tend to move toward this line of minimum circumference. The downward force generated when the absorbent article is loaded with bodily exudates also contributes to this slipping/sliding. PA1 3) Deformation of the materials of the absorbent article itself. For example, elastic elements in a diaper are subject to a property, known as stress relaxation, that is inherent in polymeric systems, such as are used as the elastic member in elastic elements of the diaper art for providing a band of tension about a wearer's waist. That is, the contractive force exerted by an elastic member decreases with time resulting in a lessening of the force exerted by the band of tension about a wearer's waist and, further, contributes to the aforementioned sagging, gapping, or slipping. Further discussion of stress relaxation can be found in many texts on polymer science, for example: Billmeyer Jr., F. W., Textbook of Polymer Science, John Wiley & Sons, pp 188-190.
The net effect of this sagging, gapping, sliding, and slipping can be premature leakage and poor fit of the absorbent article about the wearer particularly in the waist regions of the absorbent article.
In order to address premature leakage in the waist regions of absorbent articles, certain commercially available absorbent articles have been provided with elastic waist features. Such elastic waist features cause the absorbent article to fit more snugly about the waist of the wearer. An example of a disposable diaper with an elastic waist feature o which has achieved wide acceptance and commercial success is disclosed in U.S. Pat. No. 4,515,595, issued to Kievit et al. on May 7, 1985. Elastic waist features will typically comprise an elasticized waistband consisting of an elastic member contractibly affixed between the topsheet and the backsheet at the ends of the absorbent article. The elasticized waistband is, thus, designed to expand and contract with the wearer's motions and to maintain the fit of the absorbent article about the waist of the wearer during use (i.e., provide sustained dynamic fit).
However, it has been found that absorbent articles having such elastic waist features designed to fit at or near the navel also have a tendency to sag, gap, slide, or slip during use. Further, the aforementioned elastic waist feature has a tendency to rollover at the front of the diaper resulting in a lack of fit about the waist of the wearer. For male wearers, in particular, rollover increases the risk of waist leakage since a male urination stream is frequently directed toward the waist due to male anatomy.
Thus, it would be advantageous to provide an absorbent article having a waist feature that provides improved fit, reduced leakage, and enhanced wearer comfort. It would further be advantageous to provide an absorbent article which has reduced sagging, gapping, and rollover at the waist of the diaper as well as reduced overall sliding/slipping of the absorbent article or the absorbent core on the wearer during use.
Therefore, it is an object of the present invention to provide an absorbent article having sustained dynamic fit about the waist of the wearer during use.
It is a further object of the present invention to provide an absorbent article having a unique bolstering waist feature that provides sustained dynamic fit and improved resistance to leakage during use.
It is a still further object of the present invention to provide an absorbent article having a unique bolstering waist feature which reduces sagging, gapping, or rollover at the front of the diaper as well as overall sliding/slipping of the absorbent article or the absorbent core during use.
It is yet an additional object to provide an absorbent article having a unique bolstering waist feature which compensates for the loss of fit due to stress relaxation in the elastic components which provide tension about the waist region of a wearer.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings.